1. Field of the Invention
The present invention relates to techniques for cleaning, resurfacing or treating human tissue (e.g., skin) using biocompatible materials propelled into the surface of the tissue.
2. Description of Related Art
Resurfacing the human skin can be achieved by several mechanisms that are aimed primarily at disrupting the epidermal and upper dermal layers. Human skin is composed of at least three layers of variable thickness, depending upon body location. The uppermost layer, or epidermis, is usually as thin as a sheet of paper. The layer just below the epidermis is the dermis, which is largely composed of collagen and makes up the xe2x80x9cleatherxe2x80x9d layer of the skin. The dermis may vary in thickness from that of paper (50-100 xcexcm) to as thick as half an inch on the neck and back. The layer below the dermis may be composed of either muscle (around the eyes and mouth) or fat, otherwise known as subcutaneous fat
New human surface skin is regenerated following resurfacing by the surrounding islands of normal epidermis and epidermal cells migrating from the deep hair pores and other pore structures that permeate the upper dermis, mid dermis, and epidermis. If excessive scar tissue, rather than a plethora of epidermal cells, closes a surface wound, then an unsightly scar will result. The key to all resurfacing procedures is a controlled destruction of the desired area that still allows the regeneration of new tissues from pores and neighboring islands of untouched, untreated skin.
The procedures currently used in human skin resurfacing include chemical peeling, dermabrasion, laser surgery, and most recently the xe2x80x9cpower peelxe2x80x9d or crystalline peel. In chemical peeling, a caustic, disruptive or destructive liquid agent is applied to the surface skin to damage existing epidermal and dermal cells, which will then be replaced by the body. Peeling agents act depending on their strength and type. Examples of chemical peeling agents include fruit acid peel, glycolic acid peel, and trichloracetic acid (TCA) and phenol peels. TCA peels can be made to act at deeper and varying depths by varying the concentration of TCA used to destroy the surface skin. Concentrations as low as 5-10% TCA will behave similarly to a fruit acid peel, and concentrations of 50% TCA may cause severe peeling burns, which simulates phenol, and may border on scarring. Phenol, when diluted with water, penetrates more deeply and destroys more tissue than most other peeling agents.
Dermabrasion literally means abrasion of the skin and is a procedure in which a rotating sanding piece, or abrasive substance, is applied to a rigidified skin to sand out an undesirable feature, mark, or scar. Some high-speed dermabrasion rotors go up to 200,000 revolutions per minute (rpm) and do not require any rigidity to the tissues; however, they require extremely skilled personnel and special instrumentation and are impractical for most office use. A minor mistake with such a high-powered machine can have disastrous results. Dermabrasion is usually performed with a rotating wheel operating at speeds under 10,000 rpm after the skin has been rigidified using freon or dichlorotetrafluoroethane. In dermabrasion (unlike laser surgery), the person operating the abrading wheel has a direct tactile sense of pressing the wheel into the tissues being treated and can apply differential pressure to areas of elevation. Dermabrasion can be achieved to various depths depending upon the depth of freezing (rigidification), the number of passes of the abrader, the type of abrasive wheel, and the pressure applied. This procedure is waning in use, however, due to the unavailability of Freon.
Laser surgery has recently become popular to remove or reduce wrinkles, remove tumors, and alter scars, although results are mixed. Several types of lasers are used, including carbon dioxide and erbium-YAG lasers. Carbon dioxide lasers deliver light radiation at 10 xcexcm, which can vaporize and destroy surface skin. These lasers may be set on various pulse patterns to deliver precise and controlled amounts of laser radiation to the skin in a relatively uniform and homogenous fashion across the surface. An unfortunate disadvantage of this laser is that heat can be transmitted to the surrounding tissues. Additionally, after the first pass of the carbon dioxide laser, the skin begins to ooze and become wet at the surface as fluids build up in response to the damage. Since water and blood absorb in the infrared region, a second pass of the laser will penetrate to a variable depth, depending on how much surface ooze there is in the area. The ooze prevents the laser energy from reaching the target tissues uniformly. During laser irradiation, the tissues may begin to desiccate, which ultimately results in severe thermal damage. Depositing too much laser energy on the target tissues can result in persistent redness, scarring, and other complications or damage, even with thermal relaxation techniques to mitigate heat transfer.
Although other lasers, such as the erbium-YAG laser or combination CO2/erbium laser, were developed in an attempt to reduce bleeding and thermal damage, serious scarring and persistent redness can still result. If the penetration depth of the damage is complete and the regenerating skin structures are destroyed, scarring will ensue. Scarring is the unwanted presence of large amounts of collagen in the upper surface, with a minimal amount of normal appearing epidermis to lend a normal appearance to the skin. When scars are treated with certain lasers, the light does not actually remove or destroy collagen, but usually affects the hemoglobin and other blood pigments. The reduction of blood vessels to the scar causes an optical effect that makes the scar less noticeable.
Microdermabrasion (MDA) also known as xe2x80x9cThe Power Peelxe2x80x9d is a relatively new treatment patented by Molinari in U.S. Pat. No. 5,037,432. MDA has been used in Europe for the last decade. MDA is a process by which aluminum oxide crystals, which are extremely rigid, strong rasping and irregular-shaped, are projected onto the skin by air that is driven by pressures neighboring 25 pounds per square inch. Safe operation of these devices requires the use of a limited number of passes or a minimal pass speed over the target area. Most power peels are designed to remove the epidermis of the skin. However, epidermal removal will not result in any alteration of scar formation.
Almost all xe2x80x9cforeignxe2x80x9d objects are unwanted by the body. This also includes particles that are apparently inert such as sand. There are a few problems with aluminum oxide crystals and their use on the face as a peeling agent. If proper depth were attained in order to remove, destroy or alter deeper structures such as scars, pores or pits; then granuloma formation would result from the impact and placement of the aluminum oxide into the structures of the skin and the surrounding skin tissue. This is not wanted and leads to unsightly scarring. There are three main systems, of MDA used in America today; some of the systems come with a vacuum apparatus to partially suck away unwanted particles. The MDA vacuum apparatus sucks most but not all of the crystals passed. Since aluminum oxide crystals can cause foreign body reactions, even a small amount of them could be unwanted or lead to cellular difficulties later on in life. Therefore, since a MDA machine vacuum cannot be made 100 percent efficient, the power peel should not be used at a depth below the epidermis.
Two potentially serious problems have now been proposed regarding MDA. Silicosis or coal miners"" lung disease is frequently fatal; sand-like particles are spun into the air (of coal mines) coating the lungs with material that causes delayed foreign body reactions years later and interferes with breathing. In MDA the ultra-fine particles are like miniature sandspurs and are easily inhaled by the patient, thus causing a potential lung disease years from the time of exposure. Additionally, the aluminum oxide particles can deposit on the conjunctiva of the eye latching on and never letting go and causing conjunctivitis (pink eye) that may be permanent
A relatively new twist on MDA is to have a separate canister of crystallized vitamins able to be tapped and in the gas flow loop of the aluminum oxide crystals to provide the mechanical xe2x80x9cpeelingxe2x80x9d and some claimed effect of skin vitamin replenishment. Problems have arisen because any humidity in the system causes the powderized vitamins to crystallize or clump, thus clogging the microdermabrasion delivery device. The vitamin or attendant particles also do not impact on the same exact cellular location that the abrasive impacts in this type of delivery system.
WO-9937229 by Coleman et al. discloses propelling water at high speeds and pressures to cut or alter tissues. The use of water as the carrier vehicle has several major drawbacks and disadvantages. As in the time-honored process of dermabrasion (described above), freezing the skin rigid allows controlled application of energy to reduce defects. In order to immobilize skin for uniform abrasion (so that it does not deform or invaginate at treatment) temperatures well below 0 degrees Centigrade are required. Water, even when mixed with large quantities of ice cannot achieve the desired skin-immobilizing temperatures well below 0 degrees (even when not at standard pressure). Additionally, the patent by Coleman et al. would not be effective in delivering chemicals to the skin that could not be miscible with water or in solution with water unless a constant stirring mechanism was included in all portions of the Coleman system; liposomes and oil-soluble materials would separate and likely segregate into a non-uniform spray in the liquid-water-driven Coleman patent. The Coleman system would likely not uniformly expose the dermal layers so that effective application of vitamins and other medicaments could be delivered to even the upper-mid dermal layers of the skin.
Current treatments for skin at risk for infection due to thermal burns, chemical burns or other trauma or disease include removal by xe2x80x9ccold steelxe2x80x9d otherwise known as scalpel/scissor debridement and more recently by laser. By and large, debridement procedures may be painful if the nerves supplying the living tissues adjacent to the compromised tissue are still functional. This is because for the surgeon to be sure of having removed the devitalized tissues most debridement procedures are performed until bleeding is noticed (a property that is usually indicative that living/good tissue has been reached) thus ensuring that all the dead tissue has been removed. Again, dead tissue is a culture dish, lacking any antibiotics or other medicines that could halt the spread and feeding of infectious organisms.
Tissues that may need to be debrided include the largest organ (skin) following burns from fire, chemicals, blasts, etc. Also included are any exposed and damaged internal components, mostly comprising the muscle and fatty tissues just underlying the skin following blast or kinetic energy trauma. Further included may be open organs from the abdominal cavity following blast injuries, even including the bowel.
The deep but fine firing of biocompatible or bioabsorbable compounds or drugs in an aqueous vehicle, especially antibiotics (antibacterial, antiviral, anti-fungal) onto the human skin, may allow deep treatment of damaged, or devitalized skin and tissue. The device may perform the optimal multiple functions of not only removing unwanted tissues but also leaving behind desirable chemicals/medicines in order to improve the remaining tissues or prevent the growth of unwanted organisms or undesirable tissue reactions.
Thus, it would be advantageous to develop a procedure for removal of scars, wrinkles, and various other imperfections or lesions on the skin, as well as debridement of burns and cleaning of wounds, without introducing foreign bodies or substances that cause adverse physiological reactions or produce thermal damage. The present invention provides such advantages by using materials that are biocompatible.
The present invention is an apparatus for resurfacing or treating tissue using biocompatible, non-toxic materials that are propelled at the tissue with sufficient velocity to cause destruction or loosening of tissues to the desired depth upon impact. U.S. Pat. No. 6,306,119, titled xe2x80x9cSkin Resurfacing and Treatment Using Biocompatible Materialsxe2x80x9d, filed Jan. 20, 1999 is incorporated herein by reference. One objective of the invention is to propel materials into the tissue that are harmonious with the human body and thus do not cause foreign body reactions, which lead to granulomas and scarring. The materials must be hard enough (crystalline) or propelled at high enough velocities to remove tissue. Suitable resurfacing materials include solid carbon dioxide (dry ice), ice (frozen H2O), organic materials such as urea, or other amines (including amino acids) or amides, organic polymers such as sugars, carbohydrates, or proteins, and inorganic salts such as phosphates, sulfates, carbonates and nitrates. To relieve pain, a local anesthetic may be used separately or in combination with the biocompatible materials used to resurface the skin. Antibiotics could be included to prevent infection; bioabsorbable or biodegradable compounds or drugs can be delivered to the skin to treat diseases. Vasoconstrictors, such as adrenaline, can be placed into crystalline form and fired into the skin to constrict blood vessels on the surface of the skin to prevent bleeding. In addition vitamins including fat soluble (A, D, E, K) and water soluble vitamins (B complex, C), as well as co-enzymes, antioxidants, minerals, depigmenting medicines, antibiotics and other medicaments can be incorporated into the biocompatible materials.
In the present invention, the biocompatible materials are generated by abrading a solid frozen segment and propelling it through a delivery tip or nozzle to the surface of the skin or tissue to be treated. An optional vacuum system near the delivery tip can be used to remove excess materials or reaction by-products that build up on the surface of the skin. The biocompatible particles are produced at low enough temperatures to prevent the particle from melting during the delivery path to the tissue.
In one embodiment the treatment system consists of a control unit, a handheld particle generator and a cable that connects the control unit to the particle generator. The control unit can include user controls to select particle temperature, particle flux, particle velocity and vacuum. The handheld particle generator contains a mechanism to push a frozen block of biocompatible material against a rotating grinding wheel that produces small ( less than 500 micron diameter) particles. The frozen block and grinding wheel temperature can be monitored with temperature sensors integrated into the handpiece. The temperature is controlled and kept below the melting temperature of the biocompatible material. The particle density can be adjusted by controlling the speed of the grinding wheel and the speed at which the frozen block is pushed toward the grinding wheel. In normal operation the user moves the handheld device over the surface to be treated. By adjusting the particle density, particle size and particle velocity a variety of effects can be achieved.
Optional infrared temperature sensors attached to the handheld device can be used to monitor surface temperature and guide the user through the treatment. Other possible sensors include particle density and particle velocity. An accurate measurement of the particle velocity and particle size can be used to estimate the penetration depth.
An objective of the present invention is to provide an apparatus to remove scars, wrinkles, and other imperfections of the skin (or other tissue) without introducing foreign bodies or substances that cause adverse physiological reactions or produce thermal damage. Another objective of the present invention is to provide an apparatus to clean wounds and perform burn debridement. Another objective of the invention is to provide a delivery system for delivering or depositing drugs or other medications at the desired depth in the epidermis or dermis for treatment of diseased skin lesions, e.g., pre-cancers. Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings.